Background: - Hepatitis is an inflammation, irritation or swelling of liver cells from any cause.  There are different causes hepatitis among these viruses are one (A, B, C, D, and E) are the known once. Hepatitis B is a serious and common infectious disease of the liver, affecting millions of people throughout the world. So far there is no effective treatment or cure for Hepatitis B virus infection which among the public health problem in the world

Objective: - To determine Sero-prevalence and associated risk factors of hepatitis B virus among volunteer blood donors in Jimma blood bank, Jimma Southwest Ethiopia.

Method: - A cross sectional study was conducted on blood donors for HBV who attend Jimma blood bank. A total of 359 volunteer blood donors who came to Jimma blood Bank were interviewed face to face to collect socio demographic characteristics and risk factor for HBV infection, The data was analyzed using SPSS version 20.0 statistical software. Chi-square tests were used to assess associated risk factors for HBV infection.

Result; Prevalence of HBV among study participant was 3.6% From 13 participants tested positive HBV.7(3.5%) were males. The test positivity among male was 7/198 (3.54%) while among female 6/161 (3.7%) and more than three forth participants tested positive were age less than 40.After Chi-square analysis, when positivity was compared among study participants grouped based on average monthly income, participants earning 581-1,300 were less likely to have infection than participants earning below 580 Birr per month. (p=0.042). From volunteer donors, 10(2.8%) were exposed to unsafe therapeutic drug injection and from these 3(30%) were positive for HBV. When compared to volunteers who were not exposed, exposed donors were high risk of HBV infection. (p=0.000)

Conclusion Prevalence HBV of among volunteer blood donors in Jimma Blood Bank was 3.6%.     Low monthly income and using unsafe therapeutic injection were related to HBV infection.

Recommendation; Improve community awareness, infection control and post counseling will be done to control infection

Key words: hepatitis B virus, volunteer blood donor